In a general semiconductor laser, a stripe construction is added to a semiconductor crystal having a single double-heterojunction construction so that a crystal end surface forms a Fabry-Perot resonance surface.
As is known, one task imposed on this kind of semiconductor laser is to increase output. However, there is the problem of breakdown of the crystal end surface, and it is naturally limited to merely increasing a driving current for the purpose of increasing oscillation output.
In view of the foregoing, it has heretofore been proposed to make a semiconductor laser in which a plurality of stripe constructions is added to form a plurality of light emitting areas in an active layer, and the output is increased by summing the output light from the light emitting areas.
However, in the conventional semiconductor laser as just mentioned, a plurality of masking steps is required, for the addition of stripe constructions, thus making the manufacturing process complicated. Preferably, in this kind of semicondutor laser, the spacing between the light emitting areas is narrow. However, the spacing between the light emitting areas cannot be made less than the spacing limited by the photolithography technique. That is, it is difficult to increase density in the light emitting area.
Also, as is known, in a photoelectric device such as a facsimile transmitter, a photo deflector composed of an electric optical element, a movable mirror and the like combined therewith is used to scan the output light beam of a semiconductor laser.
However, the combination with the photo deflector involves many problems which are hard to solve because of complicated mechanisms. To effectively make use of the advantages of the semiconductor laser in being small and light weight, it has been desired to develop a semiconductor laser in which an element of the semiconductor laser itself has the function of scanning an output light beam.
Finally, a photo-circuit requires a photo-branch element which converts a single light beam into a plurality of light beams. Major conditions required by a photobranch element of this kind are as follows: First, that light intensity is not to be decreased by the branching. Second, that a suitable number of branch beams has to be obtained. Third, that integration or miniaturization of the photo-branch element and other photocircuit element for the photodeflector is possible.
However, a photo-branch element fulfilling these requirements has not yet been proposed. In view of the possibility of integration or miniaturization, there are the Y-branch type, the directively coupling type, etc., for example. However, in these types, the light intensity is decreased by the branching, and therefore, it is difficult to increase the number of branches.